Mercury switch



Feb 16, 1937- c. H. LARsoN MERCURY SWITCH Filed oct. 17, 1934 Patented Feb. 16, 1937 PATENT OFFICE MERCURY swrrcn Carl H. Larson, Elkhart, Ind., assignor to The Adlake Company, a corporation of Illinois Application October 17, 1934, Serial No. 748,584

4 Claims.

In mercury switches having a stationary tube 0r envelope containing electrodes and mercury displaced by an iron amature to close the circuit, there appears to be an electrolytic (or some other) action between the mercury and the iron, particularly on'inductive direct current load that makes the mercury become sluggish and apt to cling on to the amature with the result that the pick-up and drop-away values change, and other desirable characteristics lof mercury switches are lost.

The bad eilects seem to be the result of current flowing through that portion of the armature which is in the mercury.

The principal object 'of this invention is to prevent the degeneration of the switch, and this is achieved by bringing the electrodes as close together as is consistent with the necessary gap' (which varies with the voltage) and otherwisemaking any circuit through the mercury and armature of high resistance as compared with the short mercury connector between the electrodes.

'In the drawing:-

Fig. l is a vertical section through a mercury switch embodying the invention and the parts are shown in the position they assume when the magnet is energized and the mercury is forming a connector between the electrodes of the switch;

and

Fig. 2 is a view showing the parts in the position they assume when the magnet is de-energized and the mercury level has dropped to open the switch. A

But this speciiic illustration and the corresponding description are used i'or the purpose of disclosure only, and are not intended to impose limitations on theclaims, for it is realized that the gist of the invention can be variously embodied.

An envelope is, generally of glass and, preferably, low expansion glass-as disclosed in Weintraub No. 1,154,081-has sealed through it at the bottom lead-in wires Ii and i2 of tungsten, molybdenum, tantalum or the like and they are shielded by glass sleeves il and i4 up to about the middle length of the envelope. The sleeve i4 is (Cl. 20o-112) signed, also other conditions as those skilled in the art will readily recognize.

The gap between the electrodes i 5 and I 6 i's closed by purified mercury Il when the electromagnet i8 has been energized and drawn down the displacer, which is composed of a cylindrical armature I9 of ferromagnetic material, in this instance, Swedish iron known as Svea, telescoped over the entire cylinder or sleeve 20 of quartz, glass or any other ceramic or non-magnetic material that will not react with the mercury. The armature and the sleeve are held in assembled relation ,by the friction of helical springs 2i of piano wire (or any other material that will not react on the mercury) which frictionally engage the projecting ends 22 of the glass tube and extend beyond them to aiord cushions for the envelope.

In this instance there is shown between the ends of the armature i9 and the springs 2|, rings 23 having hardened steel guide fingers 24 to run along a wall of 'the envelope and guide the displacer in its movements. This, however, is a feature claimed in my copending application Serial No. 748,583, nled Oct. 17, 1934.

This particular embodiment is a front contact switch, but those skilled in the art will readily apply the principles to back contact, as well as other forms of switches.

'I'his glass envelope is approximately 110 mm. long, 15 mm. inside diameter and 17 mm. outside diameter. The top of the sleeve i3 is about 60 mm. from the base of the envelope. 'I'he other Vparts are in proportion, the drawlng'being approximately twice the size.

Fig. 1 shows the parts in approximately the position they assume when the switch is operating on closed circuit, the magnet being energized. By the magnet being de-energized, the

. displacer rises and the mercury level drops until lead-in wires sealed through the envelope. a

charge of mercurywithin the envelope, a displacer for the mercury including an iron sleeve and a sleeve of insulating material and electrodes connected with the 4lead-in wires and spaced apart but close together within the insulating sleeve, said insulating sleeve' substantially inhibiting the passage of stray current through the iron sleeve.

2. In a mercury switch, a stationary envelope,

sleeve to a. point above the low mercuryl leve1,.

the other having its contact making portion in close proximity to the corresponding part ofthe first electrode, a cylindrical iron amature telescoped over the vcontact making portions of said electrodes, and an/insulatingliner in the armature for protecting the latter from the deteriorating eect of the electric arc at the electrodes and for inhibiting stray currents from the iron armature.

4. In a. mercury switch of the type which includes an iron armature reciprocable with a switch'envelope for shifting the mercury level to change the condition of the circuit between spaced electrodes in the envelope, said electrodes being arranged so as to limit the ow of current through the mercury to a verysmall portion thereof withinithe armature whereby the remainder of the mercury can eiectively dissiof the mercury, and means for insulating the interior ofthe armature to'prevent stray currents from passing through the armature and thus contaminate the mercury by the deposit of products of electro-chemical reaction between the iron and mercury.

CARL H. LARSON.

pate the heat that is created by the resistance 

